Elevated Plasmodium Sporozoite Infection Rates in Primary and Secondary Malaria Vectors in <em>Anopheles stephensi</em>-Infested Areas of Ethiopia

Evaluating blood meal sources and sporozoite infection rates of mosquito vectors species is important to determine their role in malaria transmission. The study assessed these parameters among malaria vectors in an area recently invaded by Anopheles stephensi. Adult mosquito surveys were conducted in Hawassa, southern Ethiopia between January 2023 and April 2023. Three adult mosquito collection tools were utilized: BG-Pro Traps, CDC Light Traps, and Prokopack Aspirator. Blood meal sources and sporozoite infection rates were determined using qPCR. Overall, 738 female Anopheles mosquitoes were collected, composed of An. arabiensis (72.9%), An. pharoensis (13.4%), An. stephensi (7.5%), and An. coustani (6.2%). The Human Blood Index (HBI) was 23.3% for An. arabiensis, 43.8% for An. pharoensis, 8.3% for An. stephensi and 25.0% for An. coustani. Of the mosquitoes tested, 8% of An. arabiensis and 4.7% of An. pharoensis were Plasmodium-positive, while An. stephensi and An. coustani showed no infection. The study documented multiple efficient malaria vectors, with high Plasmodium infection rates in both primary and secondary malaria vectors, highlighting the importance of secondary vectors in malaria transmission and the need to target them in malaria vector surveillance and control efforts. The coexistence of An. stephensi alongside efficient native vectors complicates malaria control strategies, necessitating continuous monitoring to better understand their evolving roles in malaria transmission.